In recent times a world-wide energy shortage has prompted a search for non-fossil sources of energy. One obvious alternate source of energy is the production of methane gas through anaerobic digestion of organic solid wastes. Methane gas has been produced from the digestion of sewage sludge for at least 50 years in both Europe and United States. Methane has also been produced from animal wastes and used for running automobile engines and heating homes as well as for running engines and compressors at sewage plants. Thus-produced methane has two important impediments to full utilization: (1) it contains 30 to 40 percent carbon dioxide, which reduces its heating value to about 600 BTU's per cubic foot (compared to 1000 BTU natural gas), and (2) it also normally contains a small amount of hydrogen sulfide which makes it highly corrosive. The corrosive element makes the gas usable only in specifically-designed more expensive engines and makes it unsuitable for blending with pipeline-quality natural gas.
To make the gas fully compatible with pipeline gas or usable in standard engines, it may be scrubbed. There are a number of commercial processes available for removing acid gases (CO.sub.2 and H.sub.2 S), but they are all relatively expensive. Also, they do not lend themselves well to scrubbing the relatively small quantities of gas which might be produced from organic solid wastes from cities or even the wastes from a large beef cattle feedlot operation.